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The Huanghe once had a sediment flux of >1,000 Mt/yr, but this has decreased by ∼90% as its river sediment routing systems have undergone dramatic changes influenced by human activities such as dam construction. However, the way in which the sediment geochemistry of the river has responded to the altered sediment routing processes is not well known. This study investigates the sediment source‐to‐sink routing regime of the Huanghe River using Nd isotope fingerprinting. Four major source terranes, namely the Songpan‐Ganzi (SG) Block, Ordos Desert (OD), Chinese Loess Plateau (CLP) and North China Craton (NCC) are recognized according to their distinct Nd isotopes. The gradual downstream decrease in εNd values in sediments of the upper Huanghe indicates a decreasing contribution of material from the SG Block and a corresponding increase contribution of local underlying basement rocks, which is inferred to be related to sediment capture by a cascade of hydroelectric dams. A gradual increase in εNd from Yinchuan to Tongguan suggests an increasing contribution from the CLP under intense erosion. Relatively low εNd in the downstream sediments suggest a contribution from proximal NCC basement, consistent with the shift from deposition to erosion in the lower channel in recent years. The marked heterogeneity in Nd isotopes in the Huanghe sediments corresponds well to sediment source‐to‐sink processes in response to increasing human impacts. In a setting of global rivers facing strong anthropogenic impacts, the ways in which altered sediment routing systems affect river sediment geochemistry deserve more research attention. Plain Language Summary: The sediment flux of the Huanghe River (Yellow River) once exceeded 1,000 Mt/yr, but has decreased by ∼90% over the past 60 years owing mainly to the nature and intensity of human activity, during which river sediment transport processes have also changed. Here, we present Nd isotopic data for sediments from the Huanghe mainstream to investigate sediment provenances and the river sediment routing system under anthropogenic influences. Nd isotopes of potential source terrane materials allow the sediment provenances to be discriminated. The construction of cascade hydroelectric engineering projects in the upper reaches might have caused a marked decrease in sediment contribution from the Songpan–Ganzi Block, as evidenced from the gradual downstream decrease in sediment εNd in the upper reaches. The gradual increase in εNd values from Yinchuan to Tongguan suggests an increasing sediment contribution from the China Loess Plateau by intense erosion. However, relatively low εNd values in the lower reaches suggest an increased contribution of proximal sediment derived from basement of the North China Craton, with a shift from depositional to erosional processes in the lower reaches. The heterogeneity in Nd isotopes in the river sediments reveals sediment routing processes under the impact of anthropogenic activities and interventions. Key Points: Trace elements and Sr‐Nd isotopes are used to ascertain sediment provenance for modern Huanghe River in ChinaFour major source terranes are recognized and discriminated based on their unique Nd isotopic compositionsThe heterogeneity of Nd isotopes in the river sediments reveals the sediment routing regime under anthropogenic activity [ABSTRACT FROM AUTHOR]

Highlights • Magnetic method can trace the sediment provenance of the modern Yangtze River. • Paleoclimate change is dominantly controlled by the climate circulation of Pacific. • Impact from human activity is increasing since 1950s. Abstract It is essential to have a clear scientific view on paleoclimate change and its potential environmental and socio-economic impacts for the prediction of future climate change. Fluvial sediment is one of the best archives for the investigations of high-resolution environmental variability and anthropogenic impacts on catchment over the last hundreds or even thousands years (Anthropocene). In this study, we examine magnetic properties of a 130-year fluvial sediment profile from an island in the main channel of the lower Yangtze mainstream, which aims to determine the connections between modern observational data and paleoclimate signals from sediments. Sediments from the upper Yangtze River is characterized by high concentration of magnetite, which is different from the middle reach. The difference of magnetic properties allows us to trace particles in the lower reach back to upstream of the Yangtze River. Climate change that reconstructed from physical properties of sediment (susceptibility and mean grain size) is comparable to those records in historical documents, which provides a possible way to obtain precise ages. The calibrated sedimentation rate reflects long-term variation of flood/drought events over the catchment, which is dominantly controlled by the climate circulation of Pacific. The enhanced human impacts since 1950s especially in the mid-lower reaches are observed. Therefore, riverine sediment not only contains paleoclimate information, but also reflects human activities. [ABSTRACT FROM AUTHOR]

Chemical speciation of iron (Fe) in sediment offers a better understanding on iron cycle, early diagenesis, paleoredox condition and paleoclimatic changes. This study reports the Fe chemical speciation (total concentration Fe T , highly reactive Fe HR , poorly reactive Fe PR and unreactive Fe U ) in the surface sediments from the Changjiang (Yangtze River) Estuary and the East China Sea shelf. The Fe HR concentrations in the estuarine and shelf sediments are much lower than those from the Changjiang and other rivers in the world, confirming the previous observations on geochemical fractionation effect in estuarine and shelf sediments. The high correlations of Fe HR with Fe T and Al concentrations and sediment surface area, suggest the dominance of clay minerals on Fe HR composition in the sediments. The apparent enrichments of Fe HR , total organic carbon and surface area in the hypoxia zone off the Changjiang Estuary are primarily caused by the local hydrodynamics and sedimentary processes. Despite the wide application of Fe HR /Fe T ratio for redox condition, its spatial distribution from the Changjiang river mouth to open shelf reveals no obvious enrichment in the hypoxia zone. This suggests that the episodic occurrence of hypoxia off the Changjiang Estuary (mostly in August) is hardly imprinted in particulate iron speciation. The distributions of Fe chemical speciation along the “river-estuary-open shelf” transect suggest the complex controls of particulate iron “shuttle transport” and deposition in the continental margin where fluvial input dominates and intense anthropogenic impact exists. Our study sheds new light on the source-to-sink process of particulate iron in the estuary and open shelf, and also provides important constraints of Fe speciation in modern and ancient archives from various depositional environments. [ABSTRACT FROM AUTHOR]

The ultimate provenance of muddy sediment in the southwest of Cheju Island, East China Sea, remains enigmatic thus far. In this study, rare earth elements (REEs) were used to investigate sediment provenances of cores E03-6, E03-10 and E03-11 taken from the mud patch. Discrimination plots based on REE fractionation parameters and trace elements suggest that the sediments deposited during the last deglacial period (> 15 ka) were derived predominantly from the paleo-Huanghe (Yellow River) which might have delivered sediments directly into the northeastern East China Sea during the lowstand of sea level. The coarse-grained sediments deposited at transgressive stage (15–6 ka) were primarily sourced from the Changjiang (Yangtze River) and partly from the Korean Peninsula, probably transported by tidal currents. In comparison, the clayey sediments deposited at highstand stage (< 6 ka) were mostly derived from the modern and old Huanghe. In particular, the fine-grained sediments eroded from the old Huanghe Delta in the southwestern Yellow Sea can be transported to the northeast of the East China Sea by the coastal current and the Changjiang Freshwater Plume as well, and finally trapped within a cyclonic upwelling gyre. The dispersal and deposition of terrigenous sediments in the northeast of the East China Sea are remarkably controlled by the oceanic circulation related to sea level variability. The variable depositional rates and drastic river–sea interaction during the late Quaternary make it difficult to reliably reconstruct a high-resolution paleoenvironmental change in the river-dominated shelf sea. Nevertheless, geochemical approach can provide important constraints on sediment source-to-sink transport patterns in this typical pericontinental sea. [ABSTRACT FROM AUTHOR]

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The terrigenous sediment source-to-sink processes in continental margins are determined by complex interactions among climate, sediment discharge, sea level and oceanic circulations on various temporal and spatial scales. The northeastern South China Sea (NSCS) margin is a natural laboratory to catch a glimpse of these processes due to large amounts of terrigenous sediment inputs and continuous sedimentations during the late Quaternary. Based on a 35 m-long sedimentary sequence (core MD12-3429) retrieved from the NSCS upper continental slope, we distinguished sediment sources based on geochemical compositions, and then linked sedimentary responses to sea level change and Kuroshio intrusion over the past 244 kyrs via various sedimentary records including mass accumulation rates (MAR), foraminifera data, grain-size end-member modeling (EMM) and spectral analysis. Geochemical proxies including major element ratios and fractionation parameters of rare earth elements suggest that the detrital sediment in the core was derived primarily from the Taiwan. The MAR of terrigenous sediment yields an average 9.6 g/cm2/kyr, and high MAR values are both observed in glacial and interglacial intervals. The results of EMM reveal three end-members with dominant modal grain sizes of 6.6 μm (EM1), 26.3 μm (EM2) and 49 μm (EM3), respectively. The temporal variations of the finest end-member (EM1) and the coarsest end-member (EM3) demonstrate clearly glacial-interglacial cyclicity, and the spectral analysis indicates the dominance of 100-kyr eccentricity, which suggests that sea level changes are the first-order control for the NSCS continental margin sedimentation. In addition, the temporal variations in hydrodynamic sensitive component (EM2) and its MAR display gradually increasing trends with weakening East Asian monsoon. Combing with modern observation and modeling results, we suggest that enhanced Kuroshio intrusion might account for the transport of Taiwan-derived sediment during the late Quaternary. As indicated by a 31 kyr periodicity in EM2, we infer that the development of El Niño-like condition strengthened the intrusion of oligotrophic Kuroshio from the Luzon Strait, resulting in the obvious increase of Taiwan terrigenous MAR but decreases of the primary productivity in the northeastern South China Sea. This study provides deep insight into the complex terrigenous sediment source-to-sink processes in a fast-changing marginal sea environment during the late Quaternary. • Sea-level change was the primary control for terrigenous sediment source-to-sink processes in the NSCS since MIS7. • Strengthened intrusion of Kuroshio dominated Taiwan sediments transport. • Kuroshio intrusion and ENSO forcing were coupled on glacial-interglacial scale. • Grain size end-member modeling provides insights into sedimentary response to changes of sea level and oceanic circulation. [ABSTRACT FROM AUTHOR]

Abstract: Sixty-nine samples of surface sediments (0∼5 cm) recovered from the eastern Beibu Bay were analyzed for TOC and heavy metals to examine the element distribution pattern and potential pollutant sources. The sediments in the study area are characterized by variable heavy metal concentrations that are comparable with those of the surrounding regions. Obvious positive correlations were observed amongst the concentrations of Zn, Cr, Pb, Cd, Cu and the clay contents, suggesting that fine clay particles are important carriers of trace metals in the sediments. Hg and As show a considerable/low positive correlation with TOC, indicating that organic matter may play a discernible role in the sediment chemistry. Cd contamination was detected in the north of the study area primarily due to the input of phosphate fertilizers carried by rivers. In comparison, Zn, Cr, Pb, and partly Cu are predominantly sourced from lithogenic components, and Hg and As are mainly from organic matter related to anthropogenic input. [Copyright &y& Elsevier]

Abstract: The Okinawa Trough in the East China Sea continuously receives terrigenous sediments from the surrounding East Asian continent during the late Quaternary, which makes it an ideal site for the studies of land–sea interaction and sediment source-to-sink transport. Geochemical and Sr–Nd isotopic compositions of the detrital sediments in the middle Okinawa Trough allow the provenance discrimination and the reconstruction of paleoenvironmental changes over the last 30ka. Large variations in 87Sr/86Sr ratios and εNd values occur between 14.0 and 7.1ka, suggesting a significant change in sediment provenances from the dominance of the Changjiang (Yangtze River) and/or continental shelf to that of Taiwan Island. During the last glacial maximum, the continental shelf was largely exposed and the fine-grained sediments from the Changjiang and the shelf with higher 87Sr/86Sr ratios and lower εNd values might be transported directly into the middle Okinawa Trough. With the sea level rise during the deglacial period, the strengthening Kuroshio Current increasingly delivered Taiwan-derived fine sediments (lower 87Sr/86Sr ratios and higher εNd values) to the middle trough, while the sediment contribution from the East Asian continent became subordinate. This study suggests that the changes in sea level and the Kuroshio Current pathway during the late Quaternary predominantly determined the dispersal and deposition of the terrigenous sediments in the Okinawa Trough, and the Kuroshio Current might have obviously influenced the Okinawa Trough since 14ka. This study illustrates that the radiogenic isotopic compositions of the fined-grained sediments are sensitive proxies to trace the sediment provenance and to reconstruct oceanic circulations in the west Pacific marginal seas. [Copyright &y& Elsevier]

Abstract: Rivers play a key role in earth surface processes by weathering and eroding the upper continental crust under variable climate regimes. How to quantitatively determine the chemical weathering intensity in the drainage basins using geochemistry of fluvial sediments remains unclear. The Chemical Index of Alteration (CIA) and the Weathering Index of Parker (WIP) have been used worldwide as proxies to evaluate the chemical weathering intensity in large watersheds and in specific weathering profiles. In this study, concentrations of major oxides in the suspended particulate matter (SPM) and fine-grained floodplain sediments from 13 major rivers in China from north to south were analysed and compiled for the estimation of chemical weathering in China. The gradual increase in CIA and decrease in WIP values with decreasing latitude of the catchments suggest enhanced weathering intensity in these river basins. A combined monsoon climate effect of temperature, runoff and precipitation primarily controls the chemical weathering in China. The provenance rock types and relief play minor roles in weathering, whereas an active tectonic setting and typhoon events play key roles in the weathering process in Taiwan. The CIA values of the finer SPM samples within a given river are overall greater than those in the corresponding coarser floodplain sediments, underscoring the effect of sediment grain size on CIA values. The irregular seasonal variation of the CIA within a specific river further confirms the notion that the CIA does not reflect the instantaneous chemical weathering on continents. Although it is impossible to build a general model for regulating the chemical weathering of continents, this study reveals that the integrated chemical weathering intensity in large latitudinal watersheds can, with careful application, be quantitatively estimated using the proper geochemical proxies of river sediments. [Copyright &y& Elsevier]

Abstract: This study investigated the correlation of the size of detrital zircons with their age populations in a fluvial environment. From 31 floodplain sediments that were isolated from the mainstream and ten major tributaries of the Changjiang River, 3526 detrital zircon grains were selected for size examination, and 1358 were chosen for U–Pb age measurements. The Equivalent Spherical Diameter (ESD) of most zircon grains falls within the range of 32–250μm, and the dominant size is 63–125μm. Small-sized zircons with ESDs of <63μm are found in higher proportions in the mid-lower mainstream than in the upper reaches. An overall decrease in the average ESD size of detrital zircons towards the mid-lower reaches reflects the hydraulic sorting effect of different river flow regimes along this river. Overall, the age populations of zircons between the different tributaries and mainstream are similar, and several age groups correspond well with major tectonic–magmatic events that happened in the river basin. This study confirms the notion that younger zircons have coarser and more variable sizes than the older zircons, indicating the potential influence of hydrodynamic fractionation on zircon size and ages. The problem of grain-size bias on age-data acquisition and interpretation of detrital zircons from large rivers is not negligible and deserves more attention when using zircon geochronology to decipher sediment provenance and tectonic evolution. Although the zircons with an ESD of 63–125μm dominate the Changjiang sediment and have similar age populations as the bulk zircons, whether this narrow-sized window can accurately represent the bulk zircon geochronology of the weathered and heterogeneous rocks in the large catchment awaits additional investigations. [Copyright &y& Elsevier]

Abstract: The continent of China delivers huge terrigenous sediments to the East Asian marginal seas and northwest Pacific Ocean by riverine and aeolian inputs, which exerts a great impact on marine sedimentation, primary productivity and biogeochemical cycle. In this study, magnetic properties of the sediments from the Changjiang and Huanghe river systems were investigated, in order to provide potential provenance tracers. Besides, the top soil from the Loess Plateau, Taklimakan desert sand and dust storm particles were comparatively studied to reveal the controls of magnetic properties in various depositional environments. The Changjiang sediment is characterized by the highest concentration of magnetic minerals and the largest variations for most magnetic parameters, while the Huanghe sediment has much lower content of magnetic minerals. The loess soil sediment yields the highest frequency-dependent susceptibility χ fd%, while the aeolian dust has similar magnetic susceptibility but higher saturation isothermal remnant magnetization and lower anhysteretic remnant magnetization χ ARM. The desert sand has the lowest values of all magnetic parameters, indicating the lowest ferrimagnetic mineral concentration with coarser grain size. The magnetic properties of the Changjiang sediments are primarily determined by the diversity of lithology in its large drainage basin, while the sediment grain size basically accounts for the variation of magnetic parameters in the Huanghe sediment. The gradual increase of χ fd% towards the lower reaches suggests it may potentially indicate grain size fractionation in the catchments. Although some magnetic parameters can apparently discriminate the origins of fluvial and aeolian sediments, reliable magnetic proxy for distinguishing sediment origins in marine environment can only be established if hydrodynamic differentiation and post-depositional diagenetic alteration of magnetic minerals are fully understood. [Copyright &y& Elsevier]

Abstract: The late Quaternary paleoceanography and paleoenvironment in the Okinawa Trough, East China Sea, have been well reconstructed over the last decade, while in contrast the provenance of terrigenous sediments that have accumulated there remains enigmatic. In this study, rare earth elements (REE) were used to investigate provenance changes in sediments from Core DGKS9604, taken from the middle Okinawa Trough. Discrimination plots based on REE fractionation parameters suggest that the cored sediments have variable provenances over the last 30ka, with the lower part (ca. 31–8.2ka) ultimately originating mostly from the Changjiang (Yangtze River) and the upper part (7.1–0ka) primarily from Taiwan. During the Last Glacial Maximum and early deglacial period, sea level was low and the main stream of the Kuroshio Current was deflected to the east of the Ryukyu Islands. As a result the Changjiang-derived sediments might have dominated sedimentation of the middle Okinawa Trough. However, since about 7ka the main stream of the Kuroshio Current strengthened in the area of the trough, as sea level approximated the modern position. This caused near-bottom transport of fine-grained sediments from the continental margin to the trough to become weak and instead, Taiwan-derived terrigenous sediments dominated in the middle trough. The changing provenances of terrigenous sediments into the middle Okinawa Trough are closely related to the evolution of oceanic circulation and sea level in the East China Sea. Two tephra layers in the core have distinct REE compositions and correlate well with two volcanic eruptions at 7.6 and 25.8ka in southern Japan. [ABSTRACT FROM AUTHOR]

The reconstruction of paleofloods in the Holocene has become one research highlight for the present global change study. The core sediments from one newly-emerged bar in the lower Changjiang River (Yangtze River) mainstream were collected for grain size and organic elemental measurements, with aim to reconstruct the flood events over the past 150 years. Major grain size parameters such as mean grain size, probability cumulative curve and C-M diagram of the core sediments clearly indicate the flood event deposition. Furthermore, the TOC/TN ratios in the sediments can indicate flood events considering that during the flash floods, strong surface erosion in the upper and lower reaches of the Changjiang River can transport a large amount of undecomposed plant debris and organic components with relatively low C/N ratios into the lower mainstream. Based on 210Pb dating and sedimentary geochemical results, the research profile recorded several large floods happened from 1850 to 1954, which agrees well with the historical documents and hydrological observations. Interesting to note that the flood events since the 1960s cannot be distinctly recognized on the basis of sediment grain size and organic elemental compositions of the profile, which mainly reflects the intensive human activities over the last fifty years, especially condense dam construction, have significantly changed the characters of suspended sediment into the lower mainstream. [ABSTRACT FROM AUTHOR]

Detrital zircon grains of Late Cenozoic sediments dated back to ca. 3.6 Ma from core DY03 in the Yangtze delta were dated by LA-ICP-MS, in order to investigate the sedimentary provenance and to find some clue for the evolution of the Yangtze River. Most of the detrital zircon U-Pb ages are distributed at 100-300 Ma, 350-550 Ma, 600-1000 Ma, 1400-2000 Ma and 2200-2800 Ma, which correspond well with the main tectonic and magmatic events in the Yangtze drainage. The detrital zircon age patterns show distinct difference between the 3 samples below 189.8 m and other 6 above 189.8 m. 43%-55% zircons in the 3 samples below 189.8 m fall within Cretaceous, while ages from 150 to 2800 Ma are distributed with no obvious peaks, which indicate the sedimentary provenance may be limited to the lower Yangtze drainage. The 6 samples above 189.8 m show similar age patterns, and the ages are relatively evenly distributed, indicating the sedimentary provenance broadened distinctly. All 6 samples deposited later than ca. 3.2 Ma show age information from the upper Yangtze drainage (including the Emeishan large igneous province), indicating that the Three Gorges may have already been cut through by then. [ABSTRACT FROM AUTHOR]

Abstract: The Okinawa Trough is a natural laboratory for the study of later Quaternary land–ocean interaction and paleoenvironmental changes. In this study we reconstruct the evolution of clay mineral assemblages in Core DGKS9604 retrieved from the central Okinawa Trough. Illite dominates the clay mineral compositions, with average contents above 60%. Clay mineral evolution since 28ka is closely related to changes in sediment provenance and paleoenvironment. Sea level rise and the strength of the Kuroshio Current control the dispersal and deposition of clays on the East China Sea shelf and in the Okinawa Trough, and thus, determine the clay mineral compositions in the core sediments. During the late last glacial period (28.0–14.0ka), the paleo-Changjiang River mouth was situated at the shelf edge close to the central Okinawa Trough and thus, together with the outer shelf, supplied large volumes of terrigenous sediments directly into the trough. From 14.0 to 8.4ka influence from the Changjiang decreased while the mid-outer shelf of the East China Sea became the dominant sediment source to the central Okinawa Trough as sea level rose and the Changjiang river mouth migrated west. Strong sediment reworking and erosion at the shelf edge at 15–13ka significantly increased the lateral transport of fine-grained shelf sediments to the central Okinawa Trough. Since ca. 8.4ka clays from Taiwan have dominated the sediment flux to the site, coinciding with the re-entry of the Kuroshio Current into the trough. The increasing influence of the Changjiang-sourced sediments since 1.5ka was probably related to the weakening of the Kuroshio Current and/or a higher river flux. [Copyright &y& Elsevier]

Rare earth elements (REEs) of 91 fine-grained bottom sediment samples from five major rivers in Korea (the Han, Keum, and Yeongsan) and China (the Changjiang and Huanghe) were studied to investigate their potential as source indicator for Yellow Sea shelf sediments, this being the first synthetic report on REE trends for bottom sediments of these rivers. The results show distinct differences in REE contents and their upper continental crust (UCC)-normalized patterns: compared to heavy rare earth elements (HREEs), light rare earth elements (LREEs) are highly enriched in Korean river sediments, in contrast to Chinese river sediments that have a characteristic positive Eu anomaly. This phenomenon is observed also in primary source rocks within the river catchments. This suggests that source rock composition is the primary control on the REE signatures of these river sediments, due largely to variations in the levels of chlorite and monazite, which are more abundant in Korean bottom river sediments. Systematic variations in ΣLREE/ΣHREE ratios, and in (La/Yb)–(Gd/Yb)UCC but also (La/Lu)–(La/Y)UCC and (La/Y)–(Gd/Lu)UCC relations have the greatest discriminatory power. These findings are consistent with, but considerably expand on the limited datasets available to date for suspended sediments. Evidently, the REE fingerprints of these river sediments can serve as a useful diagnostic tool for tracing the provenance of sediments in the Yellow Sea, and for reconstructing their dispersal patterns and the circulation system of the modern shelf, as well as the paleoenvironmental record of this and adjoining marginal seas. [ABSTRACT FROM AUTHOR]

Abstract: A total of 71 floodplain sediments were collected from the mainstream and major tributaries of the Changjiang for heavy mineral examinations. The upper Changjiang samples contain more heavy minerals in the very fine sand fraction than the middle-lower samples which are relatively enriched in polygenetic heavy minerals. The heavy mineral assemblages are characterized by Fe–Ti oxide minerals, calcic amphibole, epidote, garnet, biotite, and zircon, which exhibit large variations in percent between different tributaries and the mainstream. The widely distributed granitoids and Permian Emeishan Basalt in the drainage basins account for the high contents of zircon and hypersthene in the Xiangjiang and Daduhe samples, respectively. Most of the detrital magnetite grains are homogeneous in typomorphic feature and almost stoichiometric in chemical composition. The discrimination plot of TiO2 +V2O3 versus MgO/(MgO+Al2O3) suggests that most of the detrital magnetite grains are sourced from felsic plutonic/volcanic and metamorphic parent rocks, and those from different tributaries have distinct chemical compositions. Our study suggests that the combination of transparent heavy mineral assemblages and varietal study of individual heavy minerals sheds new light on the provenance discrimination of the Changjiang sediments and contributes to the mineralogical determination of ancient source rocks within a large drainage basin, despite the sediment recycling and complex source rock types. [Copyright &y& Elsevier]

Elemental compositions in the surface sediments of the Yangtze River and the Yellow River are quite different. The Yangtze River's sediment is rich in K, Fe, Mg, Al and most of trace elements, and its elemental composition show remarkable spatial variations, whereas the Yellow River's sediment has higher contents of Ca, Na, Sr, Ba, Zr and Hf, and the elemental composition remains relatively stable. The ratios of some elements are also different in the sediments of the two rivers. The elemental composition of the Yangtze River sediment results from widely distributed igneous rocks and complicated source rocks and strong chemical weathering in the Yangtze River catchment basin, while the man provenance of the Yellow River sediment is the Loess Plateau which has dominant influence on the elemental composition, and the intense physical weathering is another controlling factor. The elements such as Cu, Zn Sc, Ti, Fe, V, Ni, Cr, Co, Li and element ratios such as La/Sc, La/Co, Th/Co, Ti/Zr and Zr/Y can be used as the tracers to distinguish the Yangtze River sediment from the Yellow River's. The tracers can be used in the study of the mixing and distribution of the substances of the two rivers' matters in coastal zones of China. [ABSTRACT FROM AUTHOR]

The present study conducted a comprehensive study on the distribution and source of heavy metals (Cu, Zn, Ni, Pb, Cd) in the sediments of the coastal East China Sea (ECS), one of the most developed regions in China with very active land-sea interactions, using 119 surface sediment samples and a 2-m sediment core collected after super Typhoon Chan-hom in 2015. Heavy metals in the surface sediments exhibited metal-dependent and regional distribution patterns, showing higher levels in the southern inner shelf (SIS) than the Yangtze River estuary (YRE), and generally being evaluated as unpolluted to moderately polluted in the coastal ECS (except few sites adjacent to Xiangshan Harbor were strongly polluted by Cd). Based on the organic carbon isotope compositions (δ13C) data as well as the strong correlations between heavy metals and natural major elemental contents (Al 2 O 3 , Fe 2 O 3 , and SiO 2), we suggest natural weathering detritus as the major source of heavy metals in the YRE region and the spatial distributions were highly controlled by sediment grain size and organic matter. In contrast, the spatial distributions of heavy metals in the SIS region were less correlated with sediment properties, due to more complex sources and stronger hydrodynamic impacts. The vertical distribution of heavy metals in the sediment core indicated significant enrichments since 1950s, but showed unusual gradually decreasing trends in top layer (30 cm–0.5 cm), attributing to the strong disturbance of super Typhoon Chan-hom on sediment transportation and metal partitioning. Besides, we also observed that heavy metal levels in shallow water regions of Zhejiang coast were reduced due to the passage of typhoon. Such strong impacts of super Typhoon Chan-hom on heavy metal distributions in the ECS indicates that the impacts of extreme hydrodynamic events should raise more concern when assessing the distribution and potential risks of contaminants in coastal regions. Image 1 • Natural terrestrial detritus is the major source of heavy metals in the YRE. • Cd and Cu pollution near Xiangshan Harbor should raise special attention. • Sediment grain size and organic matter controlled metal distributions in the YRE. • Metal distributions in the SIS region are impacted by complex anthropogenic inputs. • Typhoon Chan-hom reduced metals in top layer sediments in shallow water region. A comprehensive study on the distribution and source of heavy metals in the ECS, under complex geochemical and hydrodynamic (include typhoon) impacts. [ABSTRACT FROM AUTHOR]

The Zhe-Min mountainous rivers in SE China are characterized by stable tectonics, small–mesoscale drainage basins, relatively homogenous bedrocks, dense vegetation cover and high rainfall conditions. These rivers deliver loads of sediments and nutrients to the oceans and always indicate considerably high variability of sediment flux on short-term timescales. However, short-term sediment compositional variations and transport mechanism by these mountainous rivers remain poorly understood. Here we target the Minjiang River, use mineralogical and trace element geochemical data of suspended particulate matters (SPMs) within a one-year hydrological cycle (from October 2016 to October 2017), riverbed sediments (<0.063 mm fractions) and SPMs from the mainstream and major tributaries, to investigate their provenance and transport process. The results indicate that the SPMs in different seasons have strong seasonal geochemical heterogeneity, with highly positive correlations between several trace element ratios (e.g. La (CN) /Yb (CN) and Th/Sc) and runoff of the river. Riverbed sediments and SPMs collected in pairs have distinct geochemical compositions. The riverbed sediments have relatively low La (CN) /Yb (CN) (ca. 10–15) and Th/Sc (ca. 2–5) ratios, whereas the SPMs have La (CN) /Yb (CN) and Th/Sc ratio ranges of ca. 14–17 and ca. 4–7, respectively. These findings suggest a predominant hydrologic control on the Minjiang River sediment transport and geochemical compositions on a seasonal timescale. We conclude that exposed riverbed sediments are probably selectively recycled in dry-season sediment transport, whereas the flood-season SPMs are less mixed with riverbed sediments and are likely dominated by particulates directly from those tributaries and the upper mainstream. We favor that the Zhe-Min mountainous rivers are featured by rapid sediment delivery in response to hydroclimatic changes and have similar sediment transport behaviors with those small mountainous rivers in tectonically active regions of the subtropical East Asia (e.g. Taiwan). This case study also highlights the importance of multi-spatio-temporal scale, heterogeneous river input of chemical elements to the oceans. • Minjiang River sediments are investigated for mineralogy and geochemistry. • Riverbed sediments and SPMs in pairs have distinct geochemical compositions. • La/Yb and Th/Sc ratios of SPMs correlate positively with the river runoff. • Riverbed and overbank sediments are selectively recycled in dry season transport. • The river shows a hydrologic control on sediment geochemical compositions. [ABSTRACT FROM AUTHOR]

The transport time of siliciclastic sediments from their continental sites of formation to their final location of deposition on the seafloor is an important parameter bearing on land–sea interactions, climate variability and understanding of marine sediment record. 234 U/ 238 U activity ratios of the lithogenic fraction from late Quaternary sediment deposited in the Okinawa Trough, East China Sea, were reported in this study. On basis of 234 U/ 238 U activity ratios, the comminution ages and transport times were calculated using recoil loss factors ( f α ) derived from different equations based on grain size distribution. The transport times were longer (approximately 200 ± 100 kyr) for the Okinawa Trough sediments deposited between 27 and 14 ka, decreased gradually between 14 and 7 ka, and stayed relatively short (< 100 kyr) thereafter. Mineralogical, geochemical and isotopic evidences indicate that changes in sediment transport time correspond well with the shift of sediment provenance predominantly from Asia's interior prior to 14 ka to Taiwan Island after 7 ka. This study offers the first and robust constraint on time scale of sediment transport process in East Asia marginal sea, which is constrained by unique sediment source-to-sink transport pattern. The result illustrates the potential of this approach to decipher climate-related changes in the mode of supply of lithogenic sediment to marginal seas. It also highlights current difficulties in obtaining quantitative estimates of comminution age, mostly because of uncertainties in estimating the recoil loss factor. [ABSTRACT FROM AUTHOR]

In order to better interpret the signals of weathering intensity recorded in terrigenous sediment archives, it is essential to appropriately assess the effects of hydrodynamic sorting and sedimentary recycling. To achieve this, we utilized a compiled dataset of major element geochemistry of river sediments from East Asia to develop a quantitative index for evaluating the extent of quartz enrichment related to hydrodynamic sorting and sedimentary recycling. By leveraging the trend of present-cycle weathering products in the CIA-WIP diagram, we proposed the chemical index of quartz-enrichmen (CIQ), which can assess the hydrodynamic sorting and sedimentary recycling effects on the present-cycle weathering products. The CIQ vs. CIA/WIP diagram clearly discriminates the influences of weathering intensity, hydrodynamic sorting and sedimentary recycling on bulk sediment chemistry. In this diagram, representative sediments for the present-cycle weathering product typically cluster around CIQ = 0, and the CIA/WIP (or CIA) of which reflect the recorded weathering intensity. The application of our method to depth profiles from the world's largest rivers provides evidence supporting the utilization of sedimentary records to reconstruct paleo-weathering intensity. This study provides a practical and efficient approach to assess whether or to what extent siliciclastic sediments can accurately depict the present-cycle weathering products. This sheds new light on the quantitative deciphering of weathering intensity signals in terrestrial clastic sediments. • Introducing CIQ as a proxy for quartz enrichment in sedimentary processes. • Discriminating weathering, sorting, and recycling effects in sediment chemistry. • Applying our method to large river profiles validates detrital weathering proxies. [ABSTRACT FROM AUTHOR]

This study conducted a comprehensive investigation on the distribution and bioavailability of heavy metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) in sediments along two typical transects from Yangtze River to the East China Sea continental shelf that spanning large physicochemical gradients. Heavy metals were mainly associated with the fine-grained sediments (enriched with organic matter), exhibiting decreasing trends from nearshore to offshore sites. The turbidity maximum zone showed the highest metal concentrations, which evaluated as polluted for some tested metals (especially Cd) using the geo-accumulation index. Based on the modified BCR procedure, the non-residual fractions of Cu, Zn and Pb were higher within the turbidity maximum zone, and significantly negatively correlated with bottom water salinity. The DGT-labile metals all positively correlated with the acid-soluble metal fraction (especially for Cd, Zn and Cr), and negatively correlated with salinity (except Co). Therefore, our results suggest salinity as the key factor controlling metal bioavailability, which could further modulate metal diffusive fluxes at the sediment-water interface. Considering that DGT probes could readily capture the bioavailable metal fractions, and reflect the impacts of salinity, we suggest DGT technique can be used as a robust predictor for metal bioavailability and mobility in estuary sediments. [Display omitted] • Metals in sediments mainly associated with OM-enriched fine-grained particles. • The highest metal concentrations occurred within the turbidity maximum zone. • Cd exhibited the highest bioavailability among the tested metals. • Salinity was the key factor controlling metal bioavailability and mobility. • The DGT-labile metals positively correlated with the acid-soluble metal fraction. [ABSTRACT FROM AUTHOR]

Among many 234U–238U disequilibrium applications, the " comminution age " approach enabled quantitative constraints of sediment transport timescale since the genesis of detrital sediment. This method requires a critical assumption regarding the initial bedrock (234U/238U) activity ratios (A 0), typically assumed to be in secular equilibrium (=1). However, this supposition needs further validation as more authors proposed preferential leaching as a vital mechanism that produces U-series disequilibrium among bedrocks. To address this uncertainty and to examine the extent of impacts responsible for the bedrock (234U/238U) disequilibrium, we compiled the published A 0 covering a wide range of lithologies. In this study, the global A 0 values ranged from 0.700 to 1.280, with an average of only 0.981 ± 0.070 (2σ; n = 160). This widely observed 234U deficiency among global bedrocks cannot be resulted from the direct α-recoil of 234U alone but is attributed to the preferential release of 234U from the microfissures created in rock diagenetic history. To further evaluate the impact of A 0 on comminution age calculation, the Zhuoshui River (Taiwan Island) sediment comminution age was re-calculated using the newly measured A 0 from the Zhuoshui River basin, which is 0.978 on average. The newly derived comminution age was nearly three-fifths shorter than the values estimated using A 0 = 1 in the previous study. Our case study demonstrated that assuming bedrock secular equilibrium could lead to overestimated comminution age, inferring a significantly lengthier sediment transport timescale across the river basin; therefore should be carefully constrained to provide a holistic perspective of catchment-scale earth-surface processes. • Bedrocks are not always in a "closed system" due to the micro-fissures formation. • An "open system" through preferential leaching led to bedrock U-disequilibrium. • Zhuoshui River bedrock (234U/238U) is much more depleted than expected. • Comminution recalculation inferred nearly 3/5 shorter ages than assuming unity. [ABSTRACT FROM AUTHOR]

The Changjiang, the fourth longest river on Earth and the largest in Eurasia, has a complex sediment-routing system presently interrupted by the Three Gorges Dam, the world's largest hydroelectric engineering project. To study sediment-generation processes in the huge catchment and compare the different erosion patterns obtained by different methodological approaches, high-resolution petrographic and heavy-mineral analyses were performed on sands from the trunk river and its major tributaries. The frequency distributions of diverse groups of detrital amphiboles were also investigated. Rigorous statistical methods were used to define end-members, evaluate mineralogical variability, assess similarities among samples, and eventually calculate the relative contributions from each major tributary to the trunk river by forward end-member modelling of integrated compositional data. The litho-quartzose sand with few heavy minerals generated in Tibetan headwaters evolves downstream to feldspatho-litho-quartzose with medium-rank metamorphic rock fragments and moderately rich amphibole-epidote suites. Sand across the Sichuan basin and as far as the Three Gorges Dam is enriched in mafic volcanic, clinopyroxene, and carbonate grains eroded from Permian basalts and Paleozoic strata of the South China Block. The final (Yangtze) tract is characterized by litho-feldspatho-quartzose sand with moderately poor, amphibole-dominated suites with epidote, clinopyroxene, and garnet. The orogenic compositional signature acquired in the upper part of the basin is thus carried all the way to the Chinese passive margin, as observed also for the Yellow River in the north. Even after long-distance transport across wide continental areas, detrital modes thus reveal the tectonic character of the source rather than the geodynamic environment of the sink. Quantitative provenance analysis indicates that left-bank tributaries draining the Longmen and Qinlin mountains supply most of the sand reaching the East China Sea. Contributions from Tibetan headwaters are negligible, as those from right-bank tributaries in the middle-lower part of the basin. Sediment budgets and erosion patterns inferred from our integrated petrographic and heavy-mineral data set contrast with those based on detrital-zircon geochronology but agree with stream-profile analysis, revealing close correspondence with slope steepness, precipitation, stream power, tectonic activity, and frequency of major earthquakes. Sediment budgets based on amphibole groups are poorly constrained. We conclude that provenance budgets based on single-mineral species are typically unrobust, particularly because they suffer from inaccurate estimates of mineral concentration in the end-member sources. Exploring in detail a millesimal part of the sediment (typically 1/5000 in the case of zircon) is a risky strategy that may return a distorted picture of reality. [ABSTRACT FROM AUTHOR]

Human activities play an increasingly important role in shaping Earth surface and changing river geochemistry. This study presents elemental concentrations of suspended sediments collected from the water depth profiles in two hydrological years in the lower Changjiang (Yangtze) River, aiming to discern how intense dam constructions (e.g. , Three Gorges Dam) homogenize the source signals of downstream sediments in a large river basin. Our results show that sediment sources indicated by elemental ratios of Cr/Th, Co/Th and europium anomaly (Eu/Eu*) displayed seasonal changes in 2010–2011, while the seasonal variability disappeared in 2014–2015. After excluding the effects of hydrodynamic sorting and weathering processes, the waning seasonal variation can be best explained by the shift of downstream sediment source and sink roles with dam constructions. Different from the traditional view that the middle basin became the dominant source of sediment into the sea after dam constructions, we suggest that the middle basin actually act as a transition or buffer zone for the upstream-derived sediments. From a geochemical point of view, the sediments from the Changjiang River still feature a source signal of its upper basin above the Three Gorges Dam. Our study sheds new light on great and comprehensive influences of human activities on river sediment geochemistry, and highlights the need to carry out integrated studies on physical and chemical processes during sediment transfer from land to sea in fasting changing world. • A waning seasonal variation of sediment source is observed in the Changjiang River. • The middle basin act as a transition or buffer zone for upstream-derived sediments. • Intense dam constructions alter geochemical differentiations of large river systems. [ABSTRACT FROM AUTHOR]

Detrital zircon U Pb geochronology and geochemical proxies derived from immobile elements and isotopes are commonly applied to trace sediment sources because of their durability and stability in most earth surface processes and environments. However, little is known on whether these different tracers can contain identical or similar provenance signals for sediments of interest. This study presents the U Pb ages of detrital zircons from a grain-size fraction of 63–125 μm and elemental and Nd isotopic compositions for bulk sediments from the Mulanxi, a small mountainous river in southeast China. We aim to retrieve provenance signals preserved by different tracers and to test whether they are robust in discriminating the effect of sediment mixing in this tidal-dominated river. Our results show that detrital zircons in the Mulanxi catchments and estuarine have two major age groups at 90–110 Ma and 120–150 Ma. Moreover, the results of probability density plots (PDPs) suggest there is no significant difference in detrital zircon U Pb ages between the sediments from non-tidal and tidal reaches. The detrital zircon age distributions in the Mulanxi catchments are significantly different from those in the Changjiang (Yangtze River) catchments and in the inner shelf mud belt of the East China Sea which have distinct multiple age populations. A statistical multidimensional scaling (MDS) analysis suggests there is no a source-to-sink connection between the Changjiang and Mulanxi zircons. On the contrary, the geochemical proxies of Sc/Th, Cr/Th, and Nd isotopes reveal different sediment sources between the non-tidal and tidal reaches of Mulanxi, with the fine tidal-reach sediments having mixed sources from the offshore mud and the Mulanxi River, while the coarse-grained sediments from the non-tidal upstream being completely contributed by the Mulanxi. The contradictory results from these different provenance proxies suggest their implications and limitations for sediment source tracing. Detrital zircon ages can track the 'inherited' source signals of zircons and relating coarse fractions in sediments, but they are less sensitive to source changes in fine fractions than the geochemical proxies of Nd isotopes, Sc/Th and Cr/Th ratios. It is therefore essential and a prerequisite to carefully evaluate all possible factors controlling detrital sediment compositions, and to weigh the pros and cons of different tracers for sediment provenance discrimination especially in dynamic Small Mountainous Rivers (SMRs) and continental margins. • We examine the sediment provenance signals carried by different geochemical proxies. • Immobile elemental ratios and Nd isotopes can discriminate the sediment mixing in the tidal dominated river. • Detrital zircon ages cannot indicate the source signals of bulk sediments. • Grain size effect and sedimentary recycling may bias the provenance indications of different proxies. [ABSTRACT FROM AUTHOR]

• Systematic zircon ages from offshore basins of eastern China are firstly reported. • Zircon age spectra of the modern Yangtze River firstly appeared in the late Miocene. • The Yangtze River with present erosion patterns was formed in the late Miocene. The Yangtze River originates in the Tibetan Plateau and supplies tremendous sediments to the East China Sea. To date, when and how the Yangtze River was formed is still highly debated. This paper presents systematic detrital zircon U-Pb ages (3575 grain ages from a total of 29 samples) from the Cenozoic sediments of offshore basins in East China. The zircon age spectra vary significantly in the South Yellow Sea Basin, but are relatively stable in the East China Sea Shelf Basin (ECB) and significantly different from those of present-day Yangtze River (PYR) before the late Miocene. Comparisons of zircon ages with potential source terranes suggest that the ECB has received detrital sediments that PYR features since the late Miocene, whereas before that time, the sediment provenances show a North China and Korea affinity. Considering the overwhelming sediment input from the eastern Tibetan Plateau, the first occurrence of the PYR-featured sediments in the ECB in the late Miocene suggests that the Yangtze River with approximately present erosion patterns was established at that time. This agrees well with the exhumation history of the eastern Tibetan Plateau. The unique zircon ages in the Eocene to mid-Miocene sediments imply that the Yangtze River with headwaters in eastern Tibet might not exist before the late Miocene. This study provides new insights into the Yangtze River evolution although more lines of evidence are required, which is mainly because of the complex river sediment source-to-sink processes and tectonic and climatic forcings in the large catchment. [ABSTRACT FROM AUTHOR]